textproduct: Quad Cities

KEY MESSAGES

- Widespread rain is expected early Sunday morning through Sunday evening. Accumulations of 1-3 inches are likely (50-70%) along and south of Highway 34. There is a Moderate (Level 3 out of 4) Risk for excessive rainfall across northeast Missouri and west-central Illinois.

- There is a Marginal (Level 1 out of 5) Risk for severe weather on Sunday, mainly south of Highway 34. Primary threat is damaging winds.

- Weak disturbances and northwesterly flow aloft to keep temperatures comfortable and slightly below average through the end of next week.

SHORT TERM /THROUGH SUNDAY NIGHT/

Issued at 125 AM CDT Sat Jun 20 2026

Today...As a mid-level trough to our northwest clears the area, dry and cold air advection sets in as an elongated high pressure anchors over Iowa. Northwesterly surface flow around 5-10 knots will keep high temperatures tamed to the mid-70s to low 80s across our CWA despite the mostly clear skies.

Saturday Night...Split flow in the jet stream over the Great Plains allows a shortwave trough to pass underneath a building ridge over south-central Canada. A low pressure system will deepen along the Front Range of Colorado, developing a warm front across the Central Plains and Missouri. Cloud cover begins to increase overnight Saturday as cirrus outflow and mid- level clouds move in ahead of the system. Adding this and easterly flow near the surface, lows are expected to be a couple degrees higher than Friday night in the upper 50s and low 60s.

Sunday...The low pressure ejects eastward into Kansas, and the warm front inches northward as diffluent flow aloft maximizes along the Missouri-Iowa border. The HREF is in good agreement (70- 90%) at a rain shield developing over southwest Iowa along a mid- level F-gen band before propagating eastward into our CWA as early as 5AM. As the low pressure moves into northern Missouri on Saturday afternoon, the warm front will remain along the Iowa-Missouri border where there is a low-to- medium chance (30-50%) of rainfall accumulation exceeding 2 inch, especially along and south of Highway 34. North of Highway 34, there will be a sharp gradient in rainfall accumulations where areas north of Highway 30 may not even exceed a quarter of an inch (30-60% chance). This is a slight shift southward compared to the last few LREF runs, so the exact placement of the warm front (and ultimately the highest rainfall accumulation) still remains uncertain. Regardless, our southern most tier of counties will receive the heaviest rainfall which is reflected by a Moderate (Level 3 out of 4) Risk for excessive rainfall and a Flood Watch issuance. In terms of severe weather, south of Highway 34 also have the highest chances of seeing thunderstorms as MUCAPE will likely (60-80%) to exceed 100 J/kg. Combining this and 40-50 knots of 0-6 km shear, there is a Marginal (Level 1 out of 5) Risk for severe weather Sunday for areas south of Highway 34 with the primary hazard being damaging winds.

Sunday night...The low pressure moves into Illinois as the shortwave trough shifts over Iowa. Flow out of the northeast near the surface should advect in cold air as the skies clear out due to upper-level convergence.

LONG TERM /MONDAY THROUGH FRIDAY/

Issued at 125 AM CDT Sat Jun 20 2026

Monday-Tuesday...Behind the Sunday shortwave, zonal flow returns aloft, keeping conditions dry on Monday. Northerly winds at the surface will keep highs in the 70s and lows in the 50s Monday into Tuesday morning underneath partly cloudy skies. On Tuesday, the next shortwave trough digs southward into the Northern Plains. Another low pressure develops ahead of this trough across the Dakotas, but the positive tilt of the trough does not provide a lot of upper level support for deepening. This low pressure will swing southeastward with the trough, bringing PoPs back up Tuesday night along the cold front. The orientation of this system should limit the severe and even thunder potential.

Wednesday-Friday...As the low pressure from Tuesday night clears the area, a weak surface trough develops on the backside, keeping some light showers around as the positively tilted upper-level trough moves over Iowa. PoPs should drop off heading into Wednesday night as convergence aloft on the backside of the trough allows for subsidence to set in. Weak perturbations in the northwesterly flow aloft will keep diurnal-driven scattered PoPs on the table Thursday and Friday. In addition, weak northerly flow at the surface during this time period should keep highs in the 70s (70-90% chance), below average for this time of year.

AVIATION /06Z TAFS THROUGH 06Z SUNDAY/

Issued at 1230 AM CDT Sat Jun 20 2026

VFR expected overnight into Saturday with mainly clear skies. Light west winds tonight will turn to the northwest on Saturday, holding between 10-15 kts.

DVN WATCHES/WARNINGS/ADVISORIES

IA...None. IL...None. MO...None.